CN110999012B

CN110999012B - Multi-mode uninterruptible power supply system with improved power saving mode

Info

Publication number: CN110999012B
Application number: CN201880052568.4A
Authority: CN
Inventors: J-E·伯杰; T·科斯塔玛科伊; A·斯约伯格
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2017-06-19
Filing date: 2018-06-07
Publication date: 2023-05-30
Anticipated expiration: 2038-06-07
Also published as: EP3642925B1; GB201709695D0; EP3642925A1; US20210152017A1; CN110999012A; ES2868095T3; US11368047B2; WO2018234046A1

Abstract

An uninterruptible power supply-UPS-system (100, 100') operable in an energy-saving mode, comprising: a static bypass switch (110, 110 ') connected between an input connector and an output connector of the uninterruptible power supply system (100, 100') and activatable to operate the uninterruptible power supply system (100, 100 ') in a power saving mode, a number of power supply modules (120, 130, 121, 131, 120',130',121',131 ') each connected between the input connector and the output connector of the uninterruptible power supply system (100, 100') and controllable to perform reactive power compensation, and a controller (180) configured to control one or more controllable power supply modules (120, 130, 121, 131, 120',130',121', 131') according to a data input related to the reactive power compensation, the controller (180) configured to control the one or more controllable power supply modules (120, 130, 121, 131, 120',130',121', 131') according to the data input such that the uninterruptible power supply system (100, 100 ') adjusts a required reactive power compensation between a power supply connected to the input connector and a load (170) connected to the output connector in the power saving mode to obtain the required reactive power compensation, and the required reactive power supply system (100', and the required power compensation is determined based on the data input (100 ', 120') and the required reactive power compensation, 120', 131' is based on the data input.

Description

Multi-mode uninterruptible power supply system with improved power saving mode

Technical Field

The present description relates to a multi-mode UPS (uninterruptible power supply) system that may operate in a power saving mode.

Background

Fig. 1 shows a block diagram of a typical multimode UPS system 10, including a rectifier 12, an inverter 13, a battery converter 14, and a Silicon Controlled Rectifier (SCR) 11. The UPS system 10 includes an input connector for connecting it to a power system, such as a power grid 15, a battery connector for coupling the UPS system 10 to one or more rechargeable batteries 16, and an output connector for connecting it to a load 17. The input connector and the output connector may be provided for a one-phase, three-phase or generally multi-phase power supply. The power supplied to the input connector may be from a separate power source or may be from a shared power source.

The UPS system 10 may operate in a number of different modes.

In the double conversion mode, the rectifier 12 generates a DC (direct current) bus voltage from the voltage supplied to the input connector, and the inverter 13 generates an output AC (alternating current) voltage from the DC bus voltage. The battery converter 14 uses the DC bus voltage to charge one or more batteries 16. During a power outage, the battery converter 14 maintains the DC bus voltage, while the inverter 13 continues to operate as in the double conversion mode.

The UPS system 10 may also be bypassed for maintenance purposes or due to a fault. In this so-called bypass mode, the UPS system 10 provides mains current directly to the load 17 through the SCR 11. However, in bypass mode, the load 17 is not protected from the power outage.

The UPS system 10 may also support an energy saving mode. In such a mode, the UPS system 10 provides mains current directly to the load 17 through the SCR 11 and takes the DC bus voltage from the output connector. The inverter 13 and the rectifier 12 are commanded off to save power. However, when the bypass voltage exceeds its limit or there are some other conditions that prevent the UPS system 10 from being switched to the power saving mode, the UPS system 10 immediately transitions back to the double conversion mode to protect the load 17. The main reason for using the energy saving mode is to improve the operation efficiency.

The input power factor of the UPS system 10 may cause problems in the power saving mode. In the double conversion mode, the rectifier 12 may control the input power factor and the amount of reactive current may be near zero depending on the design of the UPS system 10. In the power saving mode, the UPS system 10 cannot control the power factor, a load 17 connected to the UPS output, which may draw reactive power, possibly resulting in a lower power factor for the UPS input connector. The capacitors at the input of rectifier 12 and the output of inverter 13 may also draw reactive current, and thus may contribute to a lower power factor of UPS system 10.

International patent application WO2014201309A1 discloses a multi-mode UPS system that can operate in an economy mode similar to the energy saving mode described above. In the economy mode, at least one of a rectifier and an inverter of the UPS system is activated and the at least one of the rectifier and the inverter is operable to perform at least one of DC voltage regulation, reactive power compensation, and active damping.

The US patent US 6 295 215 B1 relates to a power supply apparatus and a method of operating the same, more particularly to an AC power supply apparatus and method. Disclosed is a power supply device comprising a multi-mode DC/AC converter circuit providing a first power component, e.g. an actual power component, and a bypass circuit providing a second power component, e.g. a harmonic power component and/or a reactive power component, from an AC power source to a load. The DC/AC converter circuit may include a current-mode controlled inverter that provides reactive and harmonic currents to the load so that the bypass circuit transfers real power primarily between the AC power source and the load. In this way, the power factor and other power quality parameters of the AC power source may be maintained at desired levels.

US2005/043859A1 relates to a modular uninterruptible power supply system and a control method thereof, and more particularly to a system of parallel UPS modules with full uninterruptible power supply capability, and the same control logic and functional capabilities for controlling the parallel operation of UPS modules by arbitration process selection of a virtual host and dynamic start-up role detection. System designs have incorporated features for both decentralized processing and centralized control, distributed by utilizing dedicated control modules, and are capable of operating with one or more parallel UPS modules, providing fault tolerance and maximum redundancy, as well as reducing system-level single point failure risk to minimize the possibility of emergency and sensitive loads.

The US patent application US2012/181871A1 generally relates to control of uninterruptible power supplies. An Uninterruptible Power Supply (UPS) is disclosed that may include an inverter, a controller, and a bypass switch. In bypass mode operation, the controller operates the bypass switch to provide power from the output power source via the bypass switch at the uninterruptible power source output. The controller may also operate the inverter during online operation to regulate the inverter output voltage and provide the output voltage from the inverter at the UPS output when bypass operation is interrupted. The controller may also operate the inverter during bypass or other modes of operation to, among other things, provide power factor correction, harmonic current distortion control, and active power to charge the backup power source. In some embodiments, the controller operates the inverter to provide reactive power control and power factor correction.

Disclosure of Invention

The present specification describes an improved multimode UPS system.

According to a first aspect, an improved UPS system operable in an energy saving mode includes a plurality of power modules, each power module connected between an input connector and an output connector of the UPS system, and at least some of the power modules are controllable to perform reactive power compensation. Reactive power compensation may be performed based on data input related to reactive load compensation.

In accordance with a first embodiment, a UPS system capable of operating in an energy-saving mode is disclosed. The system includes a static bypass switch connected between an input connector and an output connector of the UPS system and activatable to operate the UPS system in an energy-saving mode, a number of power modules each connected between the input connector and the output connector of the UPS system and at least some of the power modules being controllable for reactive power compensation, and a controller configured to control the one or more controllable power modules in accordance with a data input related to reactive power compensation, the controller configured to control the one or more controllable power modules in accordance with the data input such that the reactive power flow between a power source connected to the input connector and a load connected to the output connector via the UPS system is regulated in accordance with the desired reactive power compensation when the UPS system is operating in the energy-saving mode, and the controller is configured to determine the desired reactive power compensation and determine the number of active power modules based on the data input to obtain the desired reactive power compensation.

In some embodiments, the controller may be configured to determine the number of active power supply modules by rounding up the result of the following equation to the next integer value: number of active power modules = required reactive power compensation/maximum reactive power compensation per power module.

In some embodiments, the data input may include one or more of the following data: the reactive load compensation requirement is configured; the defined equivalent capacitance of the UPS system; reactive power and/or power factor at the input side of the UPS system.

In some embodiments, the controller may be configured to calculate the required reactive power compensation based on one or more data comprised of data inputs.

In some embodiments, at least one of the controllable power modules may comprise a reactive power compensation device controllable by the controller.

In particular embodiments, the reactive power compensation device may include a rectifier and an inverter connected in series between the input connector and the output connector of the UPS system, and at least one of the rectifier and the inverter is controllable by the controller.

In some embodiments, the system may include a measurement device for measuring a power factor of a reactive power flow via the UPS system and/or a system including the UPS system and a load connected to an output connector of the UPS system.

According to a second aspect, a method for operating a UPS system in an energy saving mode is disclosed, the method comprising the steps of: the method includes obtaining data for determining a desired reactive power compensation, determining the desired reactive power compensation based on the obtained data, determining a number of power supply modules of the UPS system for the determined desired reactive power compensation, and controlling the determined number of power supply modules to achieve the determined desired reactive power compensation.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

Drawings

FIG. 1 illustrates a block diagram of a prior art multi-mode UPS system;

FIG. 2 illustrates a block diagram of an embodiment of a multi-mode UPS system; and

fig. 3 shows a flowchart of an embodiment of a control procedure for a multimode UPS system.

Detailed Description

In the following, functionally similar or identical elements may have the same reference numerals. Absolute values are shown below as examples only and should not be construed as limiting.

Fig. 2 shows a block diagram of a multi-mode UPS system, including two UPS systems 100, 100 'connected in parallel for powering a load 170, such as a server rack in a data center, connected to output connectors of the UPS systems 100, 100'. The input connectors of both UPS systems 100, 100' are connected to a power source device, such as a power grid 150.

Both UPS systems 100, 100' may be implemented identically, i.e., may include identical elements. Hereinafter, since the embodiment of the system 100' is the same, only the embodiment of the UPS system 100 will be described in detail.

The UPS system 100 includes an SCR 110 and two or more power modules connected in parallel to the SCR 110 between the input connector and the output connector of the UPS system 100. Each power supply module may include a

rectifier

120, 121 and an

inverter

130, 131 connected in series. The connection points between the

rectifiers

120, 121 and the

inverters

130, 131 include branch connections to the batteries and/or battery converters, similar to the UPS system 10 shown in fig. 1.

At least some of the power modules of the two UPS systems 100, 100 'are controllable, meaning that they may be commanded off at least in part, particularly when the UPS systems 100, 100' are operating in an energy-saving mode. At least partial command of the shutdown may be achieved in that the

rectifiers

120, 121 and/or the

inverters

130, 131 of the power supply module may be activated or deactivated by means of a corresponding control signal. Either the rectifier or the inverter or even both may be used for reactive power compensation.

Control of the rectifiers and/or inverters of the controller power modules of the UPS systems 100, 100' is performed by the controller 180. The controller 180 may be an element external to the UPS systems 100, 100' or separate from the UPS systems 100, 100', or it may be implemented as an internal element of one or more of the UPS systems 100, 100 '. The controller 180 may be implemented, for example, by a fixed or mobile computing device configured to perform control of the power module and includes a data communication connection, such as a wired or wireless LAN (local area network) connection, a USB (universal serial bus) connection, or a bluetooth connection, with the UPS systems 100, 100'. The controller 180 may also be integrated, for example, in the internal control electronics of the UPS system 100, 100', in particular it may be integrated with the power module in an integrated circuit implementing the power electronics of the UPS system. The controller 180 may be implemented by a standard processor, for example it is applied in a personal computer or a microcontroller, and may be configured by a computer program implementing a control algorithm for performing the controller tasks required for reactive power compensation. The controller 180 may also be implemented by an ASIC (application specific integrated circuit) or an FPGA (field programmable gate array).

When the UPS system 100, 100 'is operating in the energy saving mode, the SCR 110, 110' is activated so that power from the grid 150 is provided directly to the load 170. As described in the background section, the power modules of both UPS systems 100, 100' are typically commanded off in this mode to save power. However, the load 170 or the UPS system 100, 100' itself, particularly the input and/or output capacitors of the power modules, may draw reactive power Q in the energy-saving mode. The goal of the reactive power compensation is to eliminate the reactive power Q drawn so that ideally only the active power P flows in the input of the UPS system, which means that the ideal power factor is 1.

For reactive power compensation, the number of power modules is determined by the controller 180, which is not commanded to be off entirely, but remains activated or is commanded to be off only partially, for example by disabling the inverter or rectifier of the power module. The number of power supply modules for reactive power compensation versus the number of all power supply modules of the UPS system may depend on the following data inputs:

the reactive power compensation (amount) required in the energy saving mode may be a setting that can be modified according to customer needs; the reactive power compensation may then be constant and an attempt may be made to match the predetermined setting; and/or

The required reactive power compensation in energy saving mode may be determined from the reactive power drawn by the load and/or the UPS system itself, the reactive power on the UPS input and/or the power factor of the UPS system in energy saving mode; and

maximum reactive power compensation (maximum compensation per power module) that can be achieved by one power module.

The number of power supply modules required for reactive power compensation can be calculated from the data input using the following formula:

number of active power modules = reactive power compensation/maximum compensation per power module

The result of the above formula may be rounded up to the next integer value. The maximum compensation for each power module may be a configurable amount, which may be set according to the type of power module and which is known by the algorithm. In particular, it may be a value predefined in the algorithm and defining the maximum compensation possible for each power supply module.

And commanding the power module to be turned on or off according to the calculation result. If, for example, it is calculated that two power supply modules are needed for compensation, the first and second power supply modules of the UPS system may be commanded on, while the other power supply modules are commanded off. The rotation function for commanding the power modules to be turned on and off according to a predetermined scheme may also be used to reduce the pressure of individual power modules. For example, reactive power compensation may be switched from one power supply module to another power supply module, e.g., monthly. For example, if power modules 1 and 2 processed compensation in 1 month, power modules 2 and 3 would compensate in 2 months, power modules 3 and 4 compensate in 3 months, and so on.

In the energy saving mode, the input power factor of the UPS system may also be controlled by adjusting the reactive power compensation level. UPS systems may continually monitor the power factor and adjust the level of compensation in an attempt to achieve an optimal power factor. The number of active power modules may be calculated using the above formula. Since the reactive power drawn by the load may vary, the number of power supply modules commanded to open may also vary. A similar power module rotation function as described above may be used.

Next, an algorithm for controlling reactive power compensation in the energy saving mode of the UPS system 100, 100' will be described in detail with reference to a flowchart shown in fig. 3.

In step S10, the algorithm checks whether the energy saving mode of the UPS system 100, 100' is activated.

If the UPS system is operating in energy saving mode, the algorithm loads the configured reactive load compensation requirements as a data input in step S12 if, for example, the corresponding settings have been entered by the user.

In a next step S14, the algorithm loads as a further data input a defined UPS equivalent capacitance, which in particular corresponds to the aggregate capacitance of all power modules of the UPS system, in particular the aggregate capacitance of the input and output capacitors of the rectifiers and inverters comprised by the power modules.

The algorithm may also determine the reactive power of the input side of the UPS system and/or the power factor of the UPS system as data input, which may be part of the overall system, in step S16, for example by obtaining measured values of the reactive power and/or the power factor as data input from the measuring device.

It should be noted that two of the data inputs obtained in steps S12 to S16 may be optional, which means that only one data input is required for reactive power compensation. It should also be noted that steps S12 to S16 may be processed by the algorithm in another order or even simultaneously.

After the data input is obtained in steps S12 to S16, the algorithm determines the required reactive power compensation in step S18.

If the required reactive power compensation is entered as a user setting in step S12, the algorithm may directly use the setting.

If a defined equivalent capacitance of the UPS is input in step S14, the algorithm may derive therefrom the required reactive power compensation caused by the equivalent capacitance. For example, the derivation may be calculated using the following formula: q=c2pifju ^∧ 2, where Q is the reactive power to be compensated (in Var, v), C is the equivalent capacitance (in faraday, F), F is the input frequency of the UPS (in Hz), and U is the input voltage of the UPS (in volts). Since the input voltage and frequency may vary slightly, the actual measurement of the input voltage and frequency should be used in the calculation. For example, the input voltage and frequency may be measured continuously and the required reactive power compensation may be adjusted accordingly. Thus, the amount of reactive power compensation based on the equivalent capacitance is not constant, but almost because UPS systems typically only allow small variations in voltage and frequency. In an alternative approach, the required reactive power compensation may be calculated based on the nominal voltage and frequency of the UPS system, for example 230v@50hz in europe, and based thereon constant compensation is used.

If the algorithm determines the actual reactive power and/or power factor in step S16, it can infer the required reactive power compensation from these values or measured values.

In step S20, the algorithm determines the number of power supply modules necessary to achieve the determined required reactive power compensation, in particular by using the above formula, by calculating the number of power supply modules using the data inputs of steps S12 to S16.

The algorithm may use any of the data inputs obtained in steps S12, S14 and S16. In particular, the algorithm may determine the purpose of the data input based on whether it has obtained the data input in steps S12, S14 and S16, as follows:

if the algorithm does not obtain a data input in step S16, but in steps S12 and S14, it may use the data input obtained in the subsequent steps to determine the number of power supply modules to be used for reactive power compensation. The number of power supply modules determined in this way may be constant.

If the algorithm obtains the data input in step S16 and also in steps S12 and S14, the data input obtained in steps S12 and S14 may be used as a starting point for reactive power compensation, i.e. the algorithm may calculate the initial number of power supply modules for initial reactive power compensation from the data input obtained in steps S12 and S14 and may further adjust the number of modules and the reactive power compensation based on the data input obtained in step S16, e.g. based on actual measurements of reactive power and/or power factor

If the algorithm only gets data input in step S16 and not in steps S12 and S14, it may start with an initial configuration, where all power modules are commanded off and the power modules do not perform reactive power compensation. The algorithm may then determine the number of power supply modules to be used for reactive power compensation and activate the determined number of power supply modules. Thereafter, the number of power modules may be adjusted according to the actual data input obtained in step S16.

Finally, in step S22 the algorithm controls the determined number of power modules, in particular the inverters and/or rectifiers of the determined number of power modules, to compensate. For example, the algorithm may generate a control signal to deactivate the inverters of the determined number of power modules and activate the rectifiers in step S22. However, it is also possible to activate the rectifiers and inverters of the determined number of power modules, or to deactivate the rectifiers and activate the inverters.

At least some of the functions may be performed by hardware or software. In the case of a software implementation, a single or multiple standard microprocessors or microcontrollers may be used to process a single or multiple algorithms.

It should be noted that the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. Furthermore, any reference signs in the claims shall not be construed as limiting the scope of the description.

Claims

1. An uninterruptible power supply system (100, 100') operable in a power saving mode, comprising:

a static bypass switch (110, 110 ') connected between an input connector and an output connector of the uninterruptible power supply system (100, 100 ') and capable of activating operation of the uninterruptible power supply system (100, 100 ') in a power saving mode,

-a number of power supply modules (120, 130, 121, 131, 120',130',121',131 '), each connected between the input connector and the output connector of the uninterruptible power supply system (100, 100 '), and at least some of the power supply modules being controllable for reactive power compensation, and

-a controller (180) configured to control one or more controllable power supply modules (120, 130, 121, 131, 120',130',121',131 ') according to a data input related to reactive power compensation, the controller (180) being configured to control the one or more controllable power supply modules (120, 130, 121, 131, 120',130',121',131 ') according to the data input such that the uninterruptible power supply system (100, 100 ') adjusts a reactive power flow between a power supply connected to the input connector and a load (170) connected to the output connector according to a desired reactive power compensation to obtain the desired reactive power compensation, based on the data input, and the controller (180) being configured to determine the desired reactive power compensation and to determine the number of active power supply modules (120, 130, 121, 131, 120',130',121',131 ') based on the data input.

2. The uninterruptible power supply system (100, 100 ') of claim 1, wherein the controller (180) is configured to determine the number of active power supply modules (120, 130, 121, 131, 120',130',121',131 ') by rounding up the result of the following equation to the next integer value: the number of active power modules required reactive power compensation/maximum reactive power compensation per power module.

3. The uninterruptible power supply system (100, 100') of any of the preceding claims, wherein the data input comprises one or more of the following data:

-configured reactive load compensation requirements;

-a defined uninterruptible power supply system equivalent capacitance;

-reactive power and/or power factor at the input side of the uninterruptible power supply system (100, 100').

4. The uninterruptible power supply system (100, 100') of claim 3, wherein the controller (180) is configured to calculate the required reactive power compensation based on one or more data comprised of the data inputs.

5. The uninterruptible power supply system (100, 100 ') according to any of the preceding claims, wherein at least one of the controllable power modules (120, 130, 121, 131, 120',130',121',131 ') comprises reactive power compensation means controllable by the controller (180).

6. The system (100, 100 ') of claim 5, wherein the reactive power compensation device comprises a rectifier and an inverter connected in series between the input connector and the output connector of the uninterruptible power supply system (100, 100'), and at least one of the rectifier and the inverter is controllable by the controller (180).

7. Uninterruptible power supply system (100, 100 ') according to any of the preceding claims, comprising measuring means for measuring the reactive power flow via the uninterruptible power supply system (100, 100') and/or the power factor of a system comprising the uninterruptible power supply system (100, 100 ') and a load (170) connected to the output connector of the uninterruptible power supply system (100, 100').

8. A method for operating an uninterruptible power supply system (100, 100') according to any of the preceding claims in a power saving mode, comprising the steps of:

obtaining data (S12, S14, S16) for determining the required reactive power compensation,

determining the required reactive power compensation from the obtained data (S18),

-determining the number of power supply modules (120, 130, 121, 131, 120',130',121',131 ') of the uninterruptible power supply system (100, 100 ') for determining the required reactive power compensation (S20), and

-controlling the determined number of said power supply modules (120, 130, 121, 131, 120',130',121', 131') to achieve the determined required reactive power compensation (S22).